Canada should act fast to create an "ambitious" target to cut back on greenhouse gas emissions, the head of the United Nations said Friday.

Ban Ki-Moon told reporters gathered at the Commonwealth leaders' summit in Trinidad and Tobago that Ottawa should be setting an example on the world stage ahead of the G8 and G20 meetings to be held in Canada.

"Many countries, developed and developing countries, have come out with ambitious targets," Ban said.

"Therefore, it is only natural that Canada should come out with ambitious mid-term targets as soon as possible."

Canada has become the target of international criticism for reneging on its Kyoto commitments, and for refusing to sign a new agreement unless it includes commitments for developing nations to reduce their greenhouse gas emissions.

The comments from the U.N.'s secretary-general came as both France and Britain said they would support a global fund for poor countries to battle climate change.

French President Nicolas Sarkozy, who was speaking at a Commonwealth meeting, says that the fund should equal about US$10 billion annually for the next three years.

"We can no longer afford to be unambitious," Sarkozy said. "What is at stake here is the future of our planet."

Meanwhile, British Prime Minister Gordon Brown said that his nation would kick in about $1.3 billion over the next three years to get the "Copenhagen launch fund" off the ground.

The issue of the warming of the planet will continue to dominate the meeting of the Commonwealth Heads of Government, as leaders discuss the issue one last time before the much larger global summit on the issue in Copenhagen in 10 days.

Brown has said he hopes the group of diverse nations will be able to agree on a strong statement that warns of the many perils of letting climate change go unchecked.

"A strong message from the Commonwealth on the dangers of climate change can create the momentum needed for a global response at Copenhagen next month," Brown told Trinidad's Express newspaper.

However, Peter Kent, minister of state for foreign affairs, told reporters that "a deal in Copenhagen is a long shot."

Earlier in the day, the Queen urged Prime Minister Stephen Harper and other leaders from the 53-member body to regain the Commonwealth's relevance by leading the battle against climate change.

She noted that many of the people most affected by changing global temperatures live in Commonwealth nations, and they are also those least able to withstand the changes.

While the influence of the 53-nation group of mostly former British colonies has been largely eclipsed by the Group of Eight and G20, it appears some leaders think it can still influence the global debate on climate change.

Trinidad and Tobago Prime Minister Patrick Manning welcomed the attention and vowed to make progress on the issue.

"What we can do is to raise our voices politically," he said ahead of the talks. "We feel we can have some effect in influencing the discussions in Denmark."

It's expected that Canada will face ongoing criticism at the meeting for not doing enough to stop global warming -- mostly from smaller island nations who fear rising sea levels in coming decades could swamp or even wipe their countries off the map as the planet warms.

After the three-day Trinidad talks, Harper will be attending the Copenhagen summit, a decision his office announced late Thursday.

Harper, who has downplayed the possibility that any major deal on climate change will come from the Copenhagen talks, had initially said he would not be attending. He had designated Environment Minister Jim Prentice to head the Canadian delegation instead.

But when U.S. President Barack Obama announced Wednesday he would attend the climate change meeting, Harper appeared to change his mind.

The Copenhagen conference runs from Dec. 7 to 18. Obama will attend the third day; it's not clear when Harper will attend.

Pressure will be on world leaders in the Danish capital to piece together a new climate-change agreement, since the Kyoto Protocol is due to expire in 2012.

That position has dimmed hopes that developed and developing countries will be able to achieve consensus in Copenhagen.

With files from The Canadian Press